The invention concerns a facility for the thermal treatment of workpieces having a processing or heating chamber and at least one transport unit, extending essentially completely through the processing or heating chamber, with which the workpieces to be treated can be transported through the processing or heating chamber.
Facilities of the type discussed are used, for example, as soldering facilities, particularly reflow soldering facilities, as facilities for the hardening of plastics or plastic parts, or as facilities for the drying or hardening of adhesives or adhesive bonds. In particular, facilities of the type discussed are used in order to solder workpieces, particularly printed circuit boards, mounted with electronic components with these components in an electrically conductive way. For this purpose, the printed circuit boards and/or the components are already provided with solder before being introduced into the soldering facility. In the soldering facility, a targeted melting of the solder occurs, due to the temperature control, combined, for example, with an appropriate selection of an inert gas atmosphere or similar means, in the processing and/or heating chamber, whereby an electrically conductive connection between the components and the printed circuit board is formed.
The known soldering facilities of this type have the particular disadvantage that the throughput, which essentially determines the productivity, through these known soldering facilities can primarily only be increased by raising the pass-through speed. However, this requires, on the one hand, that the pass-through path be extendedxe2x80x94e. g., a doubled facility length for a doubled pass-through speedxe2x80x94and, on the other hand, for varying workloads of the facility, the process parameters, such as the pass-through speed and the temperature of the individual heating zones, must be continuously adjusted. This is uneconomical and leads, particularly for a high maximum throughput, to facilities with considerable lengths. In addition, due to the change of the process parameters, satisfactory soldering results cannot be guaranteed with the reliability required.
Proceeding from this prior art, it is the object of the present invention to create a facility of this type with which the throughput can be increased in an economical and reliable way.
The facility according to the invention has, in a way which is primarily known, a processing or heating chamber and at least one transport unit, extending essentially completely through the processing or heating chamber, with which the workpieces to be thermally treated, particularly to be soldered, such as printed circuit boards mounted with components, can be transported through the processing or heating chamber. The melting of the solder occurs in the processing or heating chamber, possibly under an inert gas atmosphere or similar means, as does, if necessary, the cooling of the soldered connections under defined temperature conditions to a specific predetermined value. According to the invention, at least two processing or heating levels are located one on top of the other in the processing or heating chamber, with each processing or heating level having at least one separate transport device for the workpieces.
In other words, this entails that the throughput through the facility can be increased according to the invention in that the workpieces can be transported through the facility and/or the processing or heating chamber in parallel to one another and essentially simultaneously. The proven process parameters such as pass-through speed and temperature distribution within the processing and heating chamber can thereby be kept, independent of the throughput, essentially constant without changing the length of the facility and, thereby, of the processing path; the increase in throughput occurs exclusively due to the parallel arrangement of practically as many processing or heating levels as desired, with, in addition, varying workloads also not leading to a significant change of these process parameters.
The temperature distribution and/or the distribution of the remaining process parameters in the direction of transport can be constant in basically any desired way. According to a preferred exemplary embodiment of the invention, however, the processing or heating chamber and/or at least one of the processing or heating levels has processing or heating zones arranged in sequence in the direction of transport. A temperature and process parameter distribution which can vary by location practically as desired can thereby be realized in a simple way.
The application of temperatures to the processing or heating chamber and/or the processing or heating levels can occur in any desired way through radiant or convective means, for example through electrical heating elements, gas burners, or the introduction of combustion gases. According to one exemplary embodiment of the invention, each processing or heating level can have at least one separate heating device, with, in addition, each processing or heating zone of each processing or heating level also being able to have a separate heating device. In contrast, it is also possible that at least two processing or heating levels, possibly also all of the processing or heating levels, have at least one joint heating device.
The invention can be realized in the simplest way by locating the processing or heating levels positioned one on top of the other in a uniform processing or heating chamber openly, i.e., essentially without separating walls or similar objects. According to a particularly preferred exemplary embodiment of the invention, however, the processing or heating levels are each implemented as a boxlike processing or heating chamber module which is essentially closed around its transverse circumference and is open on both axial sides. Control of the temperature and the other process parameters which is completely independent of the size of the overall processing and heating chamber, of the workload of the facility, and, connected with this, of the number of the processing or heating chamber modules located on top of one another can thereby be achieved, particularly in the individual processing or heating chamber modules. In addition, a modular design of the facility can thereby be realized which can easily be adjusted to the current capacity requirements. The facility preferably also has a rack-like or framework-like assembly in which the processing or heating chamber modules can be located on top of one another like a stack so that they can be exchanged and are, for example, easily insertable in appropriate holders.
A particularly economical modular design results if, as provided according to one exemplary embodiment of the invention, the transport device is an integral component of the respective processing and heating chamber module. For this purpose, the transport device can, for example, be positioned on the bottom of the respective processing or heating chamber module.
According to a particularly preferred exemplary embodiment of the invention, the facility has an elevator-like lifting device with which the processing or heating chamber modules can be brought into a position in which, in the respective position, they can be inserted into or removed from the rack-like or framework-like assembly. The soldering facility according to the invention can thus be easily and simply adjusted to higher capacity requirements through the addition of individual processing or heating chamber modules, and the reverse.
It is provided according to a further exemplary embodiment, particularly when the facility according to the invention is part of an automated production, that a distributing device is located, at the beginning and/or end of the processing or heating chamber and/or the processing or heating levels, with which the workpieces can alternatively be supplied to the respective processing or heating level and/or be brought to the height of the respective processing or heating level. The distributing device can thereby be controlled manually, sequentially, or with a program.
The distributing device can, according to one exemplary embodiment, essentially be implemented like a paternoster elevator, with the workpieces to be distributed being inserted either by hand or automatically, and then being brought into the respective position by means of endlessly circulating transport bands or chains.
The transfer from the distributing device to the respective transport device of the appropriate processing or heating chamber module can occur directly in basically any desired way. According to a further exemplary embodiment, however, a transfer device is located between the distributing device and the transport device, with which the workpiece can be transferred from the distributing device to the transport device and/or from the transport device to the distributing device.
Each processing or heating level can be implemented with a transport device which extends essentially over the entire width of the processing or heating level. However, at least two transport devices are preferably located next to one another in each processing or heating level.
The transfer device can be implemented as desired, for example as a chain or band conveyor device.
The facility according to the invention can be used basically as desired anywhere thermal treatment of workpieces is required. For this purpose, the facility can particularly be used as a soldering facility, particularly a reflow soldering facility, as a facility for the hardening of plastics or plastic parts, as a facility for the hardening or drying of adhesives or adhesive bonds, and also as a facility for the drying or hardening of lacquers or coatings.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.